The plane faces of two identical plano-convex lenses each having a focal length of 50 cm are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is

Question

Dr. Abubacker · Accepted Answer

(a) The focal length of combination is
$\frac{1}{F} = \frac{1}{f_{1}} + \frac{1}{f_{2}}$
Given, $f_{1} = 50\ cm,\ f_{2} = 50\ cm$
$	herefore\ \frac{1}{F} = \frac{1}{50} + \frac{1}{50} = \frac{2}{50}$
$\Longrightarrow F = \frac{50}{2} = 25\ cm$
Object when placed at center of curvature forms a real, inverted image of same size as object = (2$	imes 25 = 50\ cm$)

Q. The plane faces of two identical plano-convex lenses each having a focal length of 50 cm are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is

Explanation

Reviewed by Dr. Abubacker

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